Solvent dewaxing



June 3, 1941. w. sMlsLoFF SOLVENT DEWAXING Filed Aug. 22, 1939 WALTERSMISLOFF INVENTOR BY j ATTORN YS Patented June 3, 1941 SOLVENT DEWAXINGWalter Smisloff, Fishkill, N. Y., assigner to The Texas Company, NewYork, N. Y., a corporation of Delaware Application August 22, 1939,Serial N0. 291,284

Claims.

'Ihis invention relates to the separation of wax from oil andparticularly concerns a method of dewaxing mineral lubricating oil.

Broadly, the invention contemplates a method of separating wax fromhydrocarbon oil in the presence of a wax crystal regulator with adewaxing solvent liquid containing a wax anti-solvent liquid, andwherein the regulator is incorporated in the oil or Wax-bearing mixturein the form of a suspension in a small portion of a mixture of theanti-solvent liquid and water. The mixture of wax-bearing oil, solventand regulator is chilled to precipitate the wax, which may be removedfrom the chilled mixture by ltration, centrifuging, or other means. Theregulator may be dispersed in the oil or mixture of oil and solvent byheating or soaking or both heating and soaking.

The invention is applicable to dewaxing with selective dewaxing solventmixtures containing la wax anti-solvent liquid or comprising a mixtureof a wax anti-solvent liquid and a solvent liquid for oil. As examplesof wax anti-solvent liquids normally liquid ketones, including aliphaticketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone,methyl normal butyl ketone, as well as higher molecular Weight ketones,such as dipropyl ketone or mixed ketones, may be mentioned. Othersuitable anti-solvents may be used if desired. These anti-solventliquids are usually employed in conjunction with an oil solvent liquid,such as benzol, and its homologs, or other solvents, such as the lowmolecular weight aliphatic ethers.

The wax crystal regulating material may be a resinous material, such asthat known inthe trade as Plioform. It may comprise montan Wax or theactive ingredients thereof, or metallic soaps of the higher fatty acids,such as aluminum stearate. These Wax crystal regulating materials, ordewaxing aids, are generally of the type that form colloidal solutionsin benzol and are diiiicultly soluble in dewaxing solvent mixtures, suchas a mixture of methyl ethyl ketone and benzol.

The present invention involves dewaxing with a solvent containing aconstituent of the character of a ketone with the aid of a Wax crystalregulator of the foregoing character, by a procand from the separatedwax by distillation. The bulk of the solvent is distilled from eitherthe oil or the wax, in the absence of steam, so as to recover thesolvent in a dry condition. The re- Y maining portion of the solvent,however, is distilled with the aid of steam and during the steamdistillation the ketone or other Wax antisolvent liquid of thischaracter tends to form with the water a substantially constant-boilingmixture. i

Consequently, there is produced in the linal stage of the solventrecovery a substantial amount of this constant-boiling mixture which, inthe case of methyl ethyl ketone, for example, will comprise a mixture ofaround 88.6% methyl ethyl ketone and 11.4% Water. This mixture isusually subjected to prolonged settling and recycling through therecovery system.

I have discovered that this constant-boiling mixture, which issubstantially free from benzrol,

Vprovides an eiective medium with which to incorporate the wax crystalregulating material in the charge. The regulating material, in asubstantially dry powdered form, is mixed with this mixture withsuicient agitation to form a suspension and this suspension can then beincorporated in the Wax-bearing mixture prior to chilling, Whilemaintaining the regulator in the desired small particle form and inwhich form it is most eiectively dispersed in the wax-bearing mixture.

When the material is added in this suspension to the Wax-bearingmixture, agglutination or coagulation into larger particles is greatlyreduced. Experiments have indicated that it is desirable to avoid thisparticle growth on the part of the regulator since the formation oflarge particles hinders the dispersion of the regulator. Formation oflarge particles is avoided to a very large extent when the regulatingmaterial is added to the Wax-bearing mixture while in the form of asuspension in a mixture of the antisolvent and a small amount of water.

In order to demonstrate the invention more fully reference Will now bemade to the accompanying drawing showing a 110W diagram illustrating onemethod of operating the process.

Wax-bearing oil, from a source not shown, is charged through a pipe l toa charge tank or mixing tank 2. The dewaxing solvent, comprising, forexample, a mixture of about 40% methyl ethyl ketone and commercialbenzol, is conducted from a tank 3 to the tank 2. The oil and dewaxingsolvent are mixed in the proper proportion as, for example, around threeor four parts of solvent to one part of oil.

The resulting mixture is forced by a pump 4 through a pipe 5 to a heatexchanger 6. The Wax crystal regulating material, in the form of asuspension, the preparation of which will be described later, isconducted through a pipe 8 communicating with the pipe 5. The regulatingmaterial is mixed with the oil in small amount, usually around 0.1 or0.2% by Weight of the Wax bearing oil.

The heat exchanger 6 may provide a means of heating the mixture where itis desired, for example, to heat the mixture to a temperature of around1GO-170 F. prior to chilling. Onthe other hand, where such preliminaryheating is undesired, the heat exchanger 6 may provide means ofpreliminarily cooling the mixture.

The Wax bearing mixture is conducted from the heat exchanger 6 to achiller 9 wherein it isV chilled to a temperaturesuiiciently low toprecipitate the wax, and which may be in the range of around 0 F. tokminus 20 F., or even lower, depending upon the pour test desired for thefinal product.

The chilled mixture is then passed to a filter I0 wherein theprecipitated Wax is removed in the form of a iilter cake, which isdischarged through a conduit I I, while the resulting dewaxed filtrateis discharged through a conduit I2.

The dewaxed iiltrate is then passed through a heat exchanger or heaterI3 to a fractionator I4.

The fractionator I4 may be operated under any desired pressureconditions to removethe bulk of the solvent in the form of asubstantially dry vapor or distillate. The vaporized solvent is drawnoff through a condenser I5 to the tank 3 previously mentioned.

The unvaporizedportion of the oil and solvent accumulating in the bottomof. the fractionator I4 is drawn oi through a pipe I6 to a steamstripper VI'I. .The steam stripper I1 effects the removal of theremainder of the solvent. The solvent-free oil is drawn oii from thebottom of the stripper, while the vapors lcomprisingsolvent and waterare drawn oli" through a condenser'l, wherein they are condensed and theresulting condensate'is conducted to an accumulator I9.

Referring again to'the' wax iilter cake which is drawn off through theconduit I I; as indicated,

this wax cake, comprising a mixtureof wax and solvent, is passed througha heater or heat exchanger to a settling tank 2I.

In the tank 2l, the contents of which are 'inf a warm condition, somestratification occurs with the settling out'of a water layer in thebottom of the tank. v

The upper layer is drawn off through a heat exchanger 22, wherein it isheated prior to introduction to a fractionator 23. In the fractionator23 the bulk of the solvent associated with the wax is removed in arelatively dry-conditio through a pipe 24.

The remaining mixture of waxv and solvent is then drawn oir through thepipe 24 to a steam.

stripper 25, somewhatsimilar to the stripper VII. Here the remainder ofthe solvent is stripped in vapor form from the wax and removed through acondenser 26. The resulting condensate is then introduced to theaccumulator I9, along with the wet solvent recovered from the dewaxedfiltrate. i

In the accumulator I9 stratiiicationinto layers occurs. The upper layercomprises a mix- `ture of solvent and water rich in solvent, and

`composed Yof about 11.4%

this layer is drawn off through pipe 2'I and may be returned directly tothe lower portion of the tank 2| for recycling through the recoverysystem. On the other hand, it may be passed directly to the solventstorage for mixing with fresh charge.

The water layer accumulating in the bottom of the accumulator I9 issiphoned off through a pipe 28 to a receiving drum 29. From there it ispassed through a pipe 30 to a stripper 3I, wherein it is subjected tostripping with steam.

The vapor fraction formed in the stripper 3| is drawn off through acondenser 32 and resulting condensate introduced to a receiver 33. Thiscondensate comprises a constant-boiling mixture water and 88.6% methylethyl ketone. A portion of it is continuously returned to the top of thestripper 3| as a reux, While the remainder is drawn off through a pipe34 and, according to the more conventional method of operation, isreturned to the lower portion of the tank 2I for recycling through thesystem, or passed directly to the solvent storage for mixingwith freshcharge.

As indicated, the water layer separating in the bottom of the tank 2I isdrawn off through a pipe 35 communicating with the receiving drum 29,previously mentioned, and in this way subjected to further treatment.The water accumulating in the stripper 3| is drawn oiT from the bottomthrough a pipe 36 and discharged from the system.

In accordance with the present invention all, or a portion of, theconstant-boiling mixture is passed through a pipe 31 communicating witha mixing tank 38 for the-preparation of the suspension of wax crystalregulating material.

The wax crystal regulator, as, for example, resinous material, such asP1ioform, `reduced to a relatively dry' powdered form, is stored in acondenser 39, the lower portion of which comthe operation of a controlvalve 4I in the pipe `37. The suspension is drawn off from the bottom ofthe mixing tank 38by means of a pump 42, which forces it into 'the pipe5, which may be provided with suitable means, such as nozzles, foreffecting mixing between the suspension and the wax-bearing mixture.Likewise, the operation of the pump 42 may be 'coordinated with that ofthe pump 4 charging the wax-bearing mixture. f Y

The regulating material may be mixed with the methyl ethyl ketone-watermixture in' the proportion of about one part of regulator to 4rive tofifty parts of ketone-water mixture by weight. Also, if desired,additional methyl ethyl ketone, or other anti-solvent liquid, maybeadded directlyto the mixing tank 38.. The anti-solvent liquid addedmay thus comprise the usual makeup added to the dewaxing system. Theaddition of liquid in the tank 38 thereby increases the volume of liquidused to produce the dewaxing aid suspension and thus facilitate itsincorporation in the wax-bearing mixture, while retaining the particlesin a nely-divided state.

It is, of course, contemplated that other forms and arrangement ofapparatus, other than those described above, may be employed. Likewise,other operating conditions, such as those pertaining to temperatures andpressures, may be used.

Obviously many modications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. In the dewaxing of Wax bearing oil in the presence of a wax crystalregulator, which is effective in the presence of a small amount ofwater, with a dewaxing solvent which is subsequently distilled from thedewaxed oil, said solvent containing a Wax anti-solvent liquid, aportion of which during distillation from the oil, in the presence ofsteam, forms a substantially constant-boiling mixture of anti-solventand Water, the method of incorporating the regulator in the oil, Whichcomprises forming a suspension of the regulator in a portion of saidconstant-boiling mixture and mixing the resulting suspension with theWax bearing mixture prior to chilling.

2. In the dewaxing of hydrocarbon oil wherein the oil is mixed with adewaxing solvent, chilled, and the Wax separated from the chilledmixture in the presence of an added Wax crystal regulator, which iseiective in the presence of a small amount of water, the method ofadding the regulator to the oil, which comprises mixing the regulatorwith a substantially constant-boiling mixture of water and a ketoneeffective as a wax antisolvent component of a dewaxing solvent, andcommingling the resulting mixture with the wax bearing oil prior tochilling.

3. In the dewaxing of hydrocarbon oil wherein the oil is mixed with adewaxing solvent, chilled, and the wax separated from the chilledmixture in the presence of an added wax crystal regulator, which iselective in the presence of a small amount of Water, the method ofadding the regulator to the oil, which comprises mixing the regulatorwith an aliphatic ketone containing a small vamount of water suicient toform with the ketone a constant boiling mixture and incorporating theresulting mixture in the Wax bearing mixture prior to chilling.

4. In the idewaxing of hydrocarbon oil wherein the oil is mixed with adewaxing solvent, chilled, and the Wax separated from the chilledmixture in the presence of an added Wax crystal regulator, which iseffective in the presence of a small amount of water, the method ofadding the regulator to the oil comprising adding the regulator inpowdered form to methyl ethyl ketone containing around 11% of Water toform a suspension and incorporating said suspension in the wax bearingmixture prior to chilling.

5. In the dewaxing of wax bearing oil wherein the oil is dewaxed in thepresence of a wax crystal regulator, which is eilective in the presenceof a small amount of water, with a dewaxing solvent, which issubsequently distilled from the dewaxed oil for reuse, said solventcontaining a wax antisolvent liquid, a portion of which duringdistillation from the oil, in the presence of steam, forms asubstantially constant-boiling mixture of antisolvent and Water, themethod which comprises mixing the Wax bearing oil with the dewaxingsolvent, incorporating therein a suspension of a wax crystal regulatorin a portion of said constant-boiling mixture, chilling the resultingmixture to precipitate the Wax, and removing the precipitated wax in thepresence of the regulator.

6. The method, according to claim 5, in which the wax anti-solventliquid comprises an aliphatic ketone.

'7. In the dewaxing of wax bearing oil wherein the oil is dewaxed in thepresence of a wax crystal regulator, which is effective in the presenceof a small amount of water, with a dewaxing solvent, which issubsequently distilled from the dewaxed oil for reuse, said solventcontaining a Wax anti-solvent liquid, a portion of Which duringdistillation from the oil, in the presence of steam, forms asubstantially constant-boiling mixture of anti-solvent and water, thesteps which comprise mixing the oil with the dewaxing solvent,incorporating in the mixture a suspension of the wax crystal regulatorin a portion of said constant-boiling mixture, chilling the resultingmixture to precipitate the wax, removing the wax so precipitated toproduce a dewaxed mixture of oil and solvent, distilling the bulk of thesolvent from the dewaxed mixture, distilling the remainder of thesolvent therefrom in the presence of steam, forming during said steamdistillation a constant-boiling mixture of wax anti-solvent liquid and asmall amount of Water, and employing said constant-boiling mixture forpreparing the suspension of the wax crystal regulator.

8. In the dewaxing of wax bearing mineral oil in the presence of a waxcrystal regulator, which is effective in the presence of a small amountof water, with a dewaxing solvent containing a wax anti-solvent, thesteps comprising mixing the oil with the dewaxing solvent, forming asuspension of the wax crystal regulator in a constantboiling mixture ofwax anti-solvent and water, incorporating said suspension in the Waxbearing mixture, chilling the resulting mixture to precipitate the wax,and removing the precipitated wax in the presence of the addedregulator.

9. In the dewaxing of wax-bearing oil wherein the oil is dewaxed in thepresence of a wax crystal regulator, which is eiective in the presenceof a small amount of water, with a dewaxing solvent, which solvent issubsequently discharged from the dewaxed oil for reuse, said solventcontaining a low boiling aliphatic ketone, a portion of which duringdistillation from the oil, in the presence of steam, forms asubstantially constant boiling mixture of ketone and water, the stepswhich comprise mixing the oil with a dewaxing solvent comprising amixture in substantial proportions of an aliphatic ketone and anaromatic hydrocarbon selected from the group consisting of benzol andits homologs, incorporating in the mixture a suspension of the waxcrystal regulator in a portion of said constant boiling mixture,chilling the resulting mixture to precipitate the wax, removing the waxso precipitated to produce a dewaxed mixture of oil and solvent, dis-qtilling the bulk of the solvent from the dewaxed mixture, distilling theremainder of the solvent therefrom in the presence of steam, formingduring said steam distillation a constant boiling mixture of ketone anda small amount of water, and employing said constant boiling mixture forpreparing the suspension of the Wax crystal regulator.

10. 'I'he method according to claim 9 in which the aliphatic ketonecomprises methyl ethyl ketone and the aromatic hydrocarbon comprisesbenzol.

WALTER SMISLOFF.

